Snubbers for crane booms



Nov. 24, 1959 T. A. CHEESMAN SNUBBERS FOR CRANE BOOMS Filed April 19. 1955 2 Sheets-Sheet l INVENTOR.

THEODORE A CHESSMAN BY 2 Sheets-Sheet 2 T. A. CHEESMAN SNUBBERS FOR CRANE BOOMS Filed April 19, 1955 United States Patent Ofiice 2,914,312 Patented Nov. 24, 1959 SNUBBERS FOR CRANE BOOMS Theodore A. Cheesrnan, Portland, Oreg.

Application April 19, 1955, Serial No. 502,330

3 Claims. (Cl. 267-1) 1 This invention relates to boom snubbers for cranes and the like, and more particularly to a boom snubber of the hydraulic type and having a self-contained supply of fluid.

It is among the primary objects of the invention to provide a novel, simple and improved crane boom snubber adapted to yieldably engage the boom of a crane or the like so as to take up and compensate for certain normal boom movements. Another object of the invention is to provide an improved hydraulic crane boom snubber with means for preventing the accidental loss of hydraulic fluid when the snubber is lowered to an inclined position.

A further object of the invention is to provide a novel and improved hydraulic valve for use in a crane boom snubber of the type herein set forth.

It is a still further object of the invention to provide a boom snubber which has simplicity of organization, economy of construction and efficiency in operation.

The novel features that are considered characteristic of the invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together .with additional objects and advantages thereof, will best be understood from the following description of a specific embodiment when read in connection with the accompanying drawings, wherein like reference characters indicate like parts through the several figures and in which:

Figure 1 is a side view in elevation of the snubber, according to the present invention, attached to a crane and boom, the crane and boom being illustrated in broken lines;

Figure 1A is an enlarged view, partially in side elevation and partially in section, of the snubber removed from the crane;

Figure 2 is a plan view of the snubber;

Figure 3 is a sectional view taken on line 33 of Figure 1A; v

Figure 4 is an enlarged fragmentary sectional view taken on line 4-4 of Figure-1A;

Figure 5 is an enlarged fragmentary sectional view taken on line 55 of Figure 3, and

Figure 6 is a sectional view taken on line 66 of Figure 5.

Referring now' to the drawings, specifically to Figure 1, a'snubber 1,'in accordance with the present invention, comprises a hollow piston rod 5 slidable in a cylinder 8 through a stufiing box 10. The lower end 2 of thecylinder 8 has a fitting 9 for connection by a pivot-3 to a crane 4, and the free end of the hollow pistonrod 5 has a fitting 5A for connection by a pivot 6 to the boom 7 of the crane 4. The snubber 1 is similar to a hydraulic jack and, as disclosed in Patent No. 2,627,985, permits normal angular movement of the boom 7 but prevents sudden whipping movement of the boom in the event that a cable or connection is broken.

' said member.

The inner end of the piston rod 5 is closed by an end member 11, as shown in Figures 1A, 3 and 5, which has a slightly larger diameter than the piston rod 5 and forms a piston head within the cylinder 8 and defines a fluid pressure chamber 15 in the cylinder 8 and within which a Spring 38 is interposed between the member 11 and the inner wall of the lower end 2 of the cylinder 8. This end member 11 is provided with valve controlled passages 12, 13 and 14 for passing fluid between the piston 5 and cylinder 8. The valve assemblies in passages 12 and 14 permit fluid to pass from the pressure chamber 15 in the cylinder 8 into the piston rod 5 while the valve assembly in the passage 13 permits fluid to pass from the piston rod 5 into chamber 15 in the cylinder 8.

The passage 12 opens through the outer face of the end member 11 and includes a reduced port 22A opening through the inner face of said member. A plug 17, having an axial bore 16, is seated in the outer end of the passage 12 and is provided with a valve seat 18 on its inner end and surrounding the bore 16. A socket portion 23 on the end member 11 adjacent the port 22A extends longitudinally of the passage 12 toward the plug 17. A valve member 19 is movable in the passage 12 and includes a cup portion 241 having an axial stem 21 and a valve element 22, preferably of neoprene, seated in the cup portion 20. The stem 21 is slidably positioned in the socket 23 and a spring 24 surrounds the socket 23 and bears against the back of the cup portion 20, biasing the valve element 22 against the seat 18.

The passage 13 opens through the outer end face of the end member 11 and includes a reduced port 25 opening through the inner face of said member. A valve seat 27 on the end member 11 surrounds the port'25 and extends into the passage 13. A plug 39, preferably a cap plug, is seated in the outer end of the passage 13 and is provided with an axial bore 40. -A valve member 26, substantially identical to the valve member 19, is positioned in the passage 13, and has a-stem 26' which is surrounded by the sleeve 28 of a spider 28. A spring 29 is interposed between the spider 28 and the plug 39, biasing the valve member 26 into engagement with the valve seat 27. It will be noted that the ends of the spider arms and the sleeve 28' extend axially from the spider and straddle the spring 29. I

The passage 14 likewise opens through the outer end face of the end member 11 and includes a plurality of reduced ports. 35 opening through the inner face of A plug 34, having an axial bore 34' is seated in the outer end of the passage 14, and at its inner end has a seat 31 surrounding the bore 34. A valve, including a ball valve element 30 and a carrier 33 are disposed in the passage 14, the carrier including a cup portion engaging the ball element 30 and a stem portion which is surrounded by a spring 32 inter posed between the rear of the cup portion and the portions of the end member 11 surrounding the ports 35. The spring 32 is substantially heavier and has a considerably stronger resistance than the spring 24 which controls the valve member 19 in the passage 12.

At its outer free end, the piston rod 5 is provided with breather valves 36 and 37, as best shown in Fig. 4. The outer end wall 50 of the piston rod is provided with a pair of threaded bores 51, 51 in which are mounted externally threaded sleeves 52, 52" with parts of said sleeves extending outwardly beyond said end wall. The valve housings are threaded on the extended portions of the sleeves 52, 52' these housings each being composed of two cup shaped members 53, 54 and 53', 54' secured together to define valve chambers 55, 55 therebetween.

, to the operator.

The housing members 53, 53 have axial bores 56, 56 and internally extending valve seats 57, 57' for coopera tion with valve members 58, 58' within the chambers 55, 55. The valve members 58, 58' preferably are substantially identical in constructionto that of valve members 19 and 26, and the valve-members'58, "58 are biased toward their seats 57, 57 by springs 59, 59' within the chambers 55, 55. The housing members'54, 54 have axial bores 60, 60' so that passagesin communication with the interior of the piston rod 5 are provided by the bores 56, 56' and 60, 69', chambers 55, 55' and sleeves 51, 51.

The housings of the valves 36 and 37 may be identical in construction but with the members in reverse relation. Thus, in the valve 36, the'housing member 54 is mounted by its bore 60 on the sleeve 51 and the valve .seat 57 is carried by the member 53 so as to form an inlet valve into the piston rod 5. Conversely, in the valve 37, the housing member 53', having a valve seat 57 is mounted by its bore 56 on the sleeve 51', and the member 54' is carried by the member 53 so as to form an outlet from the piston rod 5.

In operation, the snubber 1 permits normal raising or lowering of the boom 7. When the boom is raised, the piston rod 5 moves into the cylinder 8 and the consequent pressure on the fluid in the chamber forces the fluid through the passage 12 into the piston rod 5, the fluid pressure forcing the valve member 19 off the seat 18. As the fluid passes into the piston rod 5, air pressure is built up within the rod until it is suflicient to open the breather valve 37 which relieves this pressure and precludes the development of suflicient air pressure to retard normal raising of the boom. The fluid pressure in the chamber 15 is not suflicient, during the normal raising of the boom 7, to unseat the ball valve 30 and open the passage 14.

Conversely, when the boom 7 is lowered, the piston rod 5 is withdrawn from the cylinder 8 and expands the chamber 15 within the cylinder. The expansion of the chamber 15 creates a suction through the passage 13 which unseats the valve member 26 from its seat 27 and sucks fluid from the piston rod 5 to the chamber 15. As the fluid is withdrawn from the piston rod 5 into the chamber 15, the air pressure within the rod 5 is reduced until the suction is sutficient to open the breather valve 36 which relieves this reduction in pressure and prevents creation of a vacuum which would retard movement of the boom. When the boom is fully lowered, any oil remaining in the piston rod is retained therein by the spring action of the breather valve 37, even though the snubber is inclined downwardly so that the oil would normally tend to flow through this breather valve.

In the operation of a boom, the danger lies in the possibility of a break in the load line so that the load is dropped and then the boom is suddenly released. In this event, the boom tends to whip backover the crane body and cause damage to the crane and injury The snubber 1 precludes any such sudden movement of the boom 1. However, the force of the boom when it whips is suflicient to snap the boom at its connection 6 with the snubber unless the fluid pressure in the chamber 15 is relieved faster than permitted by the valved passage 12.

The enlarged passage 14 permits a more rapid release of fluid from the chamber 15 when the pressure exceeds the resistance of the spring 32 seating the ball valve 30. When the boom whips, the sudden, excess pressure created in the chamber 15 not only unseats the valve 19 to escape through the passage 12, but it also unseats the ball valve 30 to escape through the passage 14.

The shock absorbing spring 38 in the chamber 15 .assists in arresting the final movement of the piston rod 5 and when the pressure in the chamber 15 is sufliciently reduced, the spring 32 forces the ball valve 30 to close the passage 14 so that-movement of the piston rod and the boom is arrested without damage. Obviously, when the piston rod 5 is extended by lowering the boom, the breather valve 36 is opened to admit air to replace the fluid passed to the chamber 15, so when the piston rod is retracted into the cylinder when the boom is raised, the breather valve 37 is opened to permit the escape of air which is replaced by the fluid passing into the rod from the chamber 15.

While but one specific embodiment of the invention is here shown and described, it will be understood that many numerous changes and modifications and the full use of equivalents may be resorted to in the practice of the invention without departing from the spirit or scope of the appended claims.

What I claim is:

l. A snubber comprising a cylinder, a hollow piston slidable in said cylinder and forming a reservoir, said piston and said cylinder jointly defining a fluid pressure chamber within the inner end of said cylinder, the inner end of said piston having passages therein placing said reservoir and pressure chamber in restricted communication, spring biased one-way valves in said passages and respectively operative in opposite directions toenable restricted flow of fluid between said chamber'and said reservoir and permit normal raisingand lowering of the boom but inhibit sudden movement of said boom, breather means in the outer end of said piston for admitting and exhausting air to and from said reservoir in accordance with the movement of fluid between said reservoir and said pressure chamber, the inner end of said piston having three passages therein with one of said passages being larger than the other two, the one-way valve in one of the two smaller passages permittingfluid flow from the reservoir to the chamber and the one-way valves in the other of the smaller passages and the larger passage permitting fluid flow from the chamber to the reservoir, the spring controlling the valve in the larger passage having a higher resistance to prevent opening of such valve during normal operation of the boom but permit and retard a surge of fluid from said chamber to said reservoir upon a sudden, accelerated movement of the boom.

2. A snubber as defined in claim 1 whereinsaid'breather means comprise a pair of spring biased one-way valves respectively disposed in opposite relation.

3. A snubber as defined in claim 1 comprising a spring mounted in said chamber between said piston and the end of said cylinder to assist in arresting movement of said piston into said cylinder.

References Cited in the file of this patent UNITED STATES PATENTS 821,359 Haeberlein May 22, 1906 1,150,925 Benner Aug. 24, 1915 1,650,680 Youse Nov. 29, 1927 1,685,750 Pfau et al. Sept. 25, 1928 2,018,312 Moulton Oct. 22, 1935 2,163,255 Binder et al. June 20, 1939 2,482,114 Labounsky Sept. 20, 1949 2,627,985 Sathre et al Feb. 10, 1953 2,668,603 Winslow Feb. 9, 1954 

